The present invention relates to the repair of turbine components. In particular, the present invention relates to a system for repairing turbine components. More particularly, the present invention relates to a method of using a system for repairing turbine components.
Turbines components, such as blades, nozzles, vanes, airfoils, tips and the like (hereinafter xe2x80x9cturbine componentsxe2x80x9d) are frequently formed from superalloys, for example, nickel-based superalloys, that have a directionally solidified single-crystal structure. The turbine components can be manufactured with defects, including cracks, surface defects, imperfections and holes. These defects must be repaired for reliable, proper, and dependable performance of the turbines. Turbine components also develop defects during service throughout their lifetime. These service-related defects may occur by wear, oxidation, and erosion. Such defects include cracks, surface defects, imperfections, and holes. These turbine component defects must be repaired for proper, dependable, and reliable operation of the turbine.
A previous defect repair method provided a repair material that filled the defect. The repair material was preferably the same material as a turbine component. The repair material was melted, and re-solidified to the turbine component at the defect site. The process was intended to provide an integral repaired structure, with a turbine defect site proximate the defect melting and re-solidifying with the repair material. Thus, repair material and the turbine component material formed a solid, one-piece repaired member.
Nickel-based superalloy repair materials are often used in a repair process for turbine components. The nickel base superalloy turbine component material will re-solidify with the nickel-based superalloy repair material to provide the turbine component with a structure similar to, and compatible with, its original metallurgical microstructure.
Repair material can take many different forms dependent on the defect. A wire repair material is often used for turbine blade tip repairs because turbine blade defects are commonly cracks and a melt feed from wire can be shaped to conform with a turbine blade tip shape. The wire repair material, also referred to as a weld wire, may be formed from a nickel-based superalloy composition for repairing a turbine component formed from a nickel-based superalloy. A nickel-based superalloy composition weld wire can be manufactured by powder metallurgy processes in conjunction with mechanically working to a wire form.
Powder metallurgy processes for producing nickel-based superalloy compositions often produce high volume fractions of strengthening precipitates, such as gamma prime (xcex3xe2x80x2) material. The xcex3xe2x80x2 material, which is produced in amounts up to about 70% by volume, makes weld wire brittle with low workability, and difficult to form into small diameter wires, and difficult to handle. The xcex3xe2x80x2 containing material is not ductile (will not exhibit plastic deformation) and will not bend. A brittle repair material is not well suited for further thermo-mechanical processing. A powder metallurgy-produced material also contains undesirable inclusions and contaminant intrinsic to powder metallurgy processes. Further, powder metallurgy produced wires are difficult to manufacture because conversion of raw material to wire uses conventional thermo-mechanical processes, which are expensive, time consuming, and generally not practical for materials with high xcex3xe2x80x2 volume fractions, for example up to about 70%.
Known powder metallurgy processes involve numerous steps and operations, including powder generation, consolidation, thermo-mechanical processing, and final grinding. The numerous steps present many opportunities for process error, such as foreign matter added during the process to contaminate the repair material. Foreign matter often leads to inclusions and contamination of the powder, which is undesirable. If a site is repaired using contaminated material, a resultant repaired site may not be acceptable, because it is not metallurgically sound. The repaired site will not be homogeneous due to the inclusions and contaminants, and an inherently weak spot may result where failure of the turbine component may occur, which, of course, is undesirable. The non-bending of brittle wire repair material also makes the wire material undesirable for a wire feed in tungsten inert gas (TIG) weld repair, where a wire is fed at a nozzle of a weld gun to melt the repair material.
A brittle repair material, such as a wire, is difficult to bend and conform to a crack-like defect without breakage. Breakage of the wire leads to discontinuities in the repair material at the repair site prior to melting. If the repair site is not full of repair material, prior to melting, due to discontinuities, the defect will not be completely filled and incomplete repaired sites may result. These incomplete repaired sites lead to voids in the repaired turbine component structure, which are undesirable.
Therefore, it is desirable to provide a powder metallurgically-produced repair material and a single-step process for forming repair material. The repair material should provide a low volume fraction of xcex3xe2x80x2 precipitates, thus making it less brittle and more ductile; and contain fewer contaminants and inclusions than materials formed by conventional powder metallurgy processes. The single-step process should produce a repair material that is amenable to further thermo-mechanical processing, such as, but not limited to swaging, wire drawing, and finishing operations. A turbine component, which is repaired with this material will be metallurgically sound due to the lack inclusions and contaminants in the repair material.
The present invention provides a system for providing a repair material and repairing a turbine component. The present invention also provides methods of using the system to repair turbine components as well.
Accordingly, one aspect of the present invention is to provide a turbine component repair system. The turbine control system comprises: a means for forming a rapidly solidified turbine repair material; and a means for melting the rapidly solidified repair material at the repair site, wherein the repair material bonds to the turbine component upon resolidification, thus repairing the turbine component.
A second aspect of the present invention is to provide a method of repairing a turbine component comprising the steps of: providing a rapidly solidified turbine repair material; disposing the rapidly solidified turbine repair material on a region of the turbine component that includes a defect to be repaired; melting the rapidly solidified repair material and a portion of the turbine component proximate to the defect; and resolidifying the rapidly solidified repair material and the portion of the turbine component, wherein the rapidly solidified repair material bonds to the portion of the turbine component, thereby removing the defect and repairing the component.
A third aspect of the invention is to provide a method for providing a rapidly solidified turbine repair material comprising the steps of molten providing a repair material and contacting the molten repair material with a peripheral surface of a rotating drum, wherein the molten repair material is cooled, thereby forming the rapidly solidified turbine repair material.
Finally, a fourth aspect of the present invention is to provide a method of repairing a turbine component comprising the steps of: providing a molten repair material; contacting the molten repair material with a peripheral surface of a rotating drum, wherein the molten repair material is cooled, thereby forming the rapidly solidified turbine repair material; obtaining the rapidly solidified repair material; disposing the rapidly solidified repair material on a region of the turbine component, wherein the region includes a defect to be repaired; melting the rapidly solidified repair material and a portion of the turbine component proximate to the defect; and resolidifying the rapidly solidified repair material and the portion of the turbine component, wherein the rapidly solidified repair material bonds to the portion of the turbine component, thereby removing the defect and repairing the turbine component.